Evaluation of liquid chromatography methods for the analysis of benzylpenicillin and its related substances

Ruggedness and robustness testing

Due to the strict regulatory requirements, especially in pharmaceutical analysis, analysis results with an acceptable quality should be reported. Thus, a proper validation of the measurement method is required. In this context, ruggedness and robustness testing becomes increasingly more important. In this review, the definitions of ruggedness and robustness are given, followed by a short explanation of the different approaches applied to examine the ruggedness or the robustness of an analytical method. Then, case studies, describing ruggedness or robustness tests of high-performance liquid chromatographic (HPLC), capillary electrophoretic (CE), gas chromatographic (GC), supercritical fluid chromatographic (SFC), and ultra-performance liquid chromatographic (UPLC) assay methods, are critically reviewed and discussed. Mainly publications of the last 10 years are considered.

Interlaboratory study of the analysis of benzylpenicillin by liquid chromatography

A liquid chromatography method for analysis of benzylpenicillin was examined in a collaborative study involving seven laboratories. The method comprised an isocratic part, which is used in the assay. The isocratic part corresponds to the assay method for benzylpenicillin used by a manufacturer. When the isocratic part is combined with gradient elution, the method is suitable for purity control. Five samples of benzylpenicillin (sodium and potassium salts) were analysed. The main component and the impurities were determined. An analysis of variance proved the absence of consistent laboratory bias. The laboratory-sample interaction was not significant. Estimates for the repeatability and reproducibility of the method, expressed as standard deviations (S.D.) of the result of the determination of benzylpenicillin, were calculated to be 0.71 and 0.80, respectively.

Evaluation of LC methods for the separation of phenoxymethylpenicillin and its related substances

Five isocratic reversed-phase liquid chromatography (LC) methods have been examined for the separation of phenoxymethylpenicillin and its related substances. A method previously selected for the analysis of benzylpenicillin gave the best selectivity. The mobile phase of this method is composed of 0.5 M phosphate buffer (pH 3.5)-water-methanol (10:50:40), the amount of organic modifier was slightly adapted when it was used with different columns. Similar selectivity is obtained not only on different C18 materials but also on C8 packings. The selectivity on poly(styrenedivinylbenzene) is less good. As method performance test a resolution test with benzylpenicillin was used. The robustness of this method was examined by applying a full factorial design to test the influence of the content of organic modifier in the mobile phase, the pH of the mobile phase, the concentration of buffer in the mobile phase and the temperature of the column. The results show that the method is robust.